ceph/src/boost/libs/signals2/include/boost/signals2/detail/result_type_wrapper.hpp

   1 // Boost.Signals2 library
   2
   3 // Copyright Douglas Gregor 2001-2004.
   4 // Copyright Frank Mori Hess 2007. Use, modification and
   5 // distribution is subject to the Boost Software License, Version
   6 // 1.0. (See accompanying file LICENSE_1_0.txt or copy at
   7 // http://www.boost.org/LICENSE_1_0.txt)
   8
   9 // For more information, see http://www.boost.org
  10
  11 #ifndef BOOST_SIGNALS2_RESULT_TYPE_WRAPPER_HPP
  12 #define BOOST_SIGNALS2_RESULT_TYPE_WRAPPER_HPP
  13
  14 #include <boost/config.hpp>
  15
  16 namespace boost {
  17   namespace signals2 {
  18     namespace detail {
  19       // A placeholder for void on compilers that don't support void returns
  20       struct void_type {};
  21
  22       // Replaces void with void_type
  23       template<typename R>
  24       struct nonvoid {
  25         typedef R type;
  26       };
  27       template<>
  28       struct nonvoid<void> {
  29         typedef void_type type;
  30       };
  31
  32       // Replaces void with void_type only if compiler doesn't support void returns
  33       template<typename R>
  34       struct result_type_wrapper {
  35         typedef R type;
  36       };
  37 #ifdef BOOST_NO_VOID_RETURNS
  38       template<>
  39       struct result_type_wrapper<void> {
  40         typedef void_type type;
  41       };
  42 #endif
  43
  44       // specialization deals with possible void return from combiners
  45       template<typename R> class combiner_invoker
  46       {
  47       public:
  48         typedef R result_type;
  49         template<typename Combiner, typename InputIterator>
  50           result_type operator()(Combiner &combiner,
  51           InputIterator first, InputIterator last) const
  52         {
  53           return combiner(first, last);
  54         }
  55       };
  56       template<> class combiner_invoker<void>
  57       {
  58       public:
  59         typedef result_type_wrapper<void>::type result_type;
  60         template<typename Combiner, typename InputIterator>
  61           result_type operator()(Combiner &combiner,
  62           InputIterator first, InputIterator last) const
  63         {
  64           combiner(first, last);
  65           return result_type();
  66         }
  67       };
  68     } // end namespace detail
  69   } // end namespace signals2
  70 } // end namespace boost
  71
  72 #endif // BOOST_SIGNALS2_RESULT_TYPE_WRAPPER_HPP